A rear projection method projector device, in other words, a rear projection system is known. The rear projection method displays an image area on a front side of a screen by transmitting light that is projected from a rear side of the screen by a projector device to the front side of the screen where a viewer is positioned.
Japanese Laid-Open Patent Publication No. 05-233148 discusses a projector device with a coordinate input function to detect a position specified by a user on a screen displayed by the rear projection method. The projector device having the coordinate input function includes a video camera that picks up a rear side of a screen installed at substantially the same position as the projector. Moreover, a lens of the video camera is provided with a filter that typically passes a bright spot of a laser beam of light that transmits from a front side to a rear side of the screen. The projector device with the coordinate input function uses a coordinate input unit such as a laser beam pointer to specify a coordinate on the screen. The coordinate input unit and the filter allow the video camera to output an image that typically includes a bright spot by the coordinate input unit.